Conventionally, in railway vehicles, and especially in railway vehicles that travel at high speed, there are concerns that the noise generated in, and in the vicinity of, a device, especially a power collector, disposed on the roof of the vehicle may be increased by the increase in speed of the railway vehicles, so in order to insulate such noise, acoustic insulation bodies which are placed with a distance from the rooftop device in a width direction of the vehicle body and having a given length along the longitudinal direction of the vehicle body are provided on the roof.
On the other hand, in Shinkansen (bullet train) lines that are designed to be able to travel through conventional railway sections, such as miniature Shinkansens which travel from Shinkansen tracks directly to conventional railway lines, wherein the conventional railway lines have the track gauge converted from a narrow track for conventional railways to a standard gauge, the critical range of the vehicle body is narrow, so that the restrictions related to the width of the vehicle body or the height of the vehicle body are strict compared to Shinkansen sections, and in order to cope with such restrictions, there are demands for downsizing the device for insulating (blocking) the noise generated from the devices disposed on the roof of the vehicle.
In order to reduce or insulate the noise generated from devices such as the power collector disposed on the roof of the vehicle body of a mobile vehicle, an art of covering the vicinity of the power collector with a wind cover and providing an acoustic insulation wall for insulating noise to the outer side of the wind cover is already proposed, and an acoustic insulation device as disclosed in patent literature 1 is already proposed. In other words, an acoustic insulation device for a mobile vehicle having a simple configuration and having a high sound insulating effect is proposed, that fits within the critical range of vehicles in a conventional railway section, and that enables to ensure sufficient insulation distance between the acoustic insulation panel and the power collector. The acoustic insulation means is composed of first and second acoustic insulation bodies provided upright in a chevron-shape in a width direction of the vehicle body with respect to a device on the roof and having a predetermined length along a longitudinal direction of the vehicle body, wherein the first acoustic insulation body is arranged rearward to the second acoustic insulation body with respect to a direction of travel of the mobile vehicle.
Further, there is proposed a soundproof wall that is used as a side wall for roads, railways, factories and so on, that exerts sufficient soundproof effect not only for the nose that travels upward from a low area, but for the noise that travels downward from the upper area (patent literature 2). The soundproof wall illustrated in patent literature 2 has a first bifurcation wall that is inclined to a noise source side at an upper end of a main wall that extends upward, and a second bifurcation wall that is inclined to an opposite side from the noise source side, wherein at least one bifurcation wall out of the first and second bifurcation walls has a re-bifurcation wall that is re-bifurcated to a direction that differs from said bifurcation wall.
However, the soundproof wall taught in patent literature 2 is a soundproof wall that is provided at a fixed location such as on the ground, and there is no consideration on placing the wall on a railway vehicle that travels at a high speed. Therefore, it is difficult to apply the soundproof wall simply to a railway vehicle to realize a design that fits within the critical range of the vehicle. In addition, if there is a need to provide a means for insulating noise generated from a power collector of the railway vehicle, an insulation distance (the range of distance in which an object cannot be placed for insulation) with respect to the high voltage section of the power collector must be ensured, so that it is difficult to satisfy this request according to the method taught in patent literature 2.
In a railway vehicle, the main noise source is the power collector disposed on the roof of the vehicle. The acoustic insulation device of a mobile vehicle according to patent document 1 has been developed to block the noise generated from the power collector efficiently. The acoustic insulation device for a mobile vehicle is disposed to block the main source of noise that appears on a downstream side of the direction of flow of the noise source from an observer of the noise (or local residents) considering the direct advancing property of sound. However, sound not only has a direct advancing property, but it also has a reflecting or diffracting property. As for the noise generated from a power collector of the mobile vehicle, a portion of the noise is reflected or diffracted to come around the sound insulation wall and reaches the observer of the noise (or local residents).